You don't say in the OP whether when you upgraded to 200/20 it was for a fixed term, e.g. 12 months, but it's pretty standard practice for there to be early termination fees applied to any contract or plan. I'd be very surprised if it wasn't in the T&Cs.

When you upgrade or move to a different plan then you usually go onto a new fixed term contract - it would have been there in black and white somewhere when you requested the speed increase. The fees that you could have been charged for upgrading would have been absorbed as you were going onto a new 12 month contract.

There is nothing Stealth about it - this is how broadband contracts operate - fixed term.

There are wholesale fee's involved with moving between UFB speed profiles, to put it simply we absorb the cost of an upgrade (and recoup it through the new plan eventually) and charge part of the downgrade.

One thing worth noting here is that our contracts are for services with us and are irrespective of service type of speed plan, so no new contract term or anything like that would have been entered with a speed change, and there is no requirement to remain on the new speed for any period of time.